1S47.] 



at Madras, 



161 



with certainty at any time divest the reading of the Barometer of 

 the immediate solar influence, and thus be able to say what the at- 

 mosphere effect alone amounts to : — these hourly changes will be 

 rendered graphically intelligible by the annexed drawing, but will 

 be more immediately useful, as exhibited in the following table : 



Corrections to he applied to the Barometrical reading to reduce it to 

 its mea}% Indication. 



Mean Time. 



Correction. 



Mean Time. 



Correction. 



h. m. 



In. 



h. 



m. 





In. 



0 -41 P.M. 



+0-004 



0 



•41 



A. M. 



- 0^00 4 



1 -41 — 



4-0-032 



1 



•41 





4-0-C12 



2 -41 — 



4-0-053 



2 



•41 





4-0-022 



3 -41 — 



4-0-062 



3 



•41 





4-0-024 



4 -41 — 



4-0-050 



4 



•41 





4-0-016 



5 -41 — 



4-0-013 



5 



•41 





4-0-001 



6 -41 — 



4-0-027 



6 



•41 





—0-018 



7 -41 — 



4-0-001 



7 



-41 





-0-033 



8 -41 — 



-40-017 



8 



-41 





—0-054 



9 -41 — 



—0-029 



9 



•41 





—0-055 



10 -41 — 



-0-029 



10 



•41 





—0-044 



11 -41 — 



—0-019 



11 



•41 





—0 022 



With regard to the thermometer, the mean of the hourly obser- 

 vations in each month, together with the mean maximum, and mean 

 minimum Table II., is all that the present limits will admit. Instead 

 of giving the indications of the wet bull thermometer as heretofore, 

 • — I have given (Table III.), a column exhibiting the humidity of 

 the air with reference to unity (1), the point of perfect saturation. 

 In this table too is given the depth to which rain has fallen as well 

 as the amount of evaporation from a surface of water. 



Table IV. exhibits the number of hours in each month (as derived 

 from an Osier's Anemometer), during which the wind has prevailed 

 from the N. W., S. W., S. E. or N. E. qa;irter, or has approximat- 

 ed to either of these, by which a fair estimate can be formed of the 

 general direction of the wind ; in Table V., is given the mean as 

 well as the extreme force of the wind as exhibited by its action on a 

 flat surface of metal when disposed so as immediately to oppo?e its 

 direction ; the numbers set down, represent the number of pounds 

 avoirdupoise, with which the wind presses on a square foot of surface, 

 these being derived from direct measurement by the Anemometer, 

 are necessarily free from the uncertainty, to which personal estima- 

 tions are liable. 



w 



